"At this point there's people that are certainly acting up, and we're doing our best to take them into custody," Nelson said shortly after 9:30 p.m.

He said authorities have begun arresting protesters.

Police have issued an unlawful assembly order and made several arrests in downtown, police Chief Anthony Batts said.

At about 8 p.m., a crowd began moving toward a police line that had been held for several hours and threw rocks and bottles at the officers, Batts said.

He said the unruly crowd was comprised of about 50 people wearing black masks, black hooded sweatshirts and backpacks.

Batts described them as anarchists and said their goal was to go into crowds and cause people on both sides to overact.

Police issued a dispersal order and said over a loudspeaker that the protest had been declared an unlawful assembly, Batts said.

"Most people did disperse, but a number did not," he said.

Police tried to push the crowd north, away from downtown, to minimize damage, Batts said. Officers also began making arrests.

Looting and vandalism were reported at some businesses, though.

A Foot Locker at 14th Street and Broadway was broken into and robbed, and members of the crowd broke the windows of a Far East National Bank, according to witnesses.

Batts said the remaining protesters were there for "bad reasons."

"We're taking our time, pushing, allowing them to leave," he said. "There will probably be more arrests."

Batts said no injuries had been reported for several hours.

Earlier in the evening, a woman was hit by a police car bumper when the car was backing up through a crowd.

The car was moving at a slow speed, and the woman suffered a minor injury. Batts said police would follow up with her.

Mayor Ron Dellums said he was pleased with the police response so far. He added that both sides have shown restraint in moments of anguish.

"I want to thank the residents of Oakland who went out there to express themselves passionately, vocally, even angrily, but in a way that was respectful of Oscar Grant, his family and the community," he said.

Tony Coleman, a community organizer with Oakland Assembly and the New Years Movement for Justice for Oscar Grant, said the violence was preceded by a peaceful, productive rally.

"The speak-out was a total success, everybody got a chance to speak. We did our thing," Coleman said.

The speeches were heartfelt and emotional, he said.

"It was going so good, we left at a high point, and that way folks will be more interested in maybe coming to the community meeting," Coleman said.

He said the group will hold a meeting next Thursday at the Continental Club at 1658 12th St. to discuss the next steps in light of the verdict.